The present invention relates to pistons.
In particular, the present invention relates to pistons of the type which are used to serve as gas-operated pistons of firearms.
As is well known it is conventional to provide certain types of firearms with gas-operated pistons. Such a piston is displaced by part of the gas resulting from the firing of a projectile, so that the energy resulting from the explosion in the firearm is used to move the gas piston. This movement of the gas piston is utilized in a known way to cock the firearm automatically in preparation for firing the next round. Thus, with such a firearm upon firing of one round part of the gas under pressure is deflected from the barrel to a gas-operated piston which is displaced to cock the firearm and place it in a condition ready for firing the next round.
Pistons of this type are subject to extremely great stresses. Thus in the above example when a round is fired the gas piston is subject to a considerable impact stress, this stress being a variable magnitude as a result of the different magnitudes or strengths of the charges which are fired. A piston of the above general type is required to have a fluid-tight sliding engagement with outer and inner cylindrical surfaces. For manufacturing purposes such a piston has a substantially rigid part fluid-tightly engaging one of these surfaces and an elastic sealing ring which engages the other of these surfaces. Thus, by providing a construction where the piston includes interconnected rigid and elastic components for respectively fluid-tightly and slidably engaging coaxial cylindrical surfaces one of which surrounds the other, it is possible to simplify the manufacture since precise coaxial relationships between the sealing surfaces of the piston need not be maintained and thus maintenance of extremely strict manufacturing tolerances can be avoided. However, while the manufacturing of pistons including a pair of such components provides certain advantages, there are disadvantages in that up to the present time no satisfactory structure has been found to maintain the piston components reliably assembled with each other. Thus, in view of the stresses which are encountered during operation considerable difficulty has been encountered in maintaining the elastic sealing ring properly assembled with the rigid part of the piston. As a result, conventional assemblies cannot withstand the large impact stresses over a long period of time, and the result is that the sealing ring of the piston does not remain properly assembled with the rigid part of the piston so that a desired seal is not maintained and the assembly comes apart in time to such an extent that proper operation cannot be assured and repairs are required.